Female die assembly for attaching a self-attaching fastening element and method of attachment

Abstract

A self-attaching fastening element, such as a nut fastener, having a body portion and an integral annular riveting barrel portion. The body portion includes axial grooves and, in the preferred embodiment of the nut-type fastener, the body portion includes a radial flange and the grooves extend radially from the body portion into the flange portion. In the most preferred embodiment, the body portion is polygonal and the axial grooves are located in the juncture of adjacent flat surfaces. The method of attaching the self-attaching fastening element of this invention to a panel includes forming an opening in the panel coaxially aligned with the barrel portion having a diameter less than the barrel portion, driving the barrel portion into the panel, thereby drawing a cone-shaped portion in the panel receiving the body portion, driving the body portion into the cone-shaped panel portion, deforming the panel portion into the body portion and the axial grooves. The free end of the barrel portion may be simultaneously deformed radially to form a mechanical interlock with the panel. Where the body portion includes a radial flange, the flange is driven into the panel and the panel is driven into the radial grooves, preventing relative rotation of the fastening element in the panel.

Having thus described the improved self-attaching fastening element, method of installation and installation apparatus of this invention, the invention is now claimed, as follows: 
     
       1. A method of attaching a female fastening element in a plastically deformable panel, said fastening element including a polygonal body portion having a generally cylindrical bore therethrough and an integral plastically deformable annular riveting barrel portion having an inner surface coaxially aligned with said bore of said body portion and an outer surface having a diameter less than a major diameter of said polygonal body portion, said polygonal body portion having an external surface including a plurality of flats and axial grooves defined in said body portion in the juncture of adjacent flats, said method comprising the following steps: forming an opening in said panel coaxially aligned with said inner surface of said annular riveting barrel portion having a diameter less than the diameter of said inner surface of said annular barrel portion,   driving said barrel portion into said panel, drawing said panel into a cone-shaped panel portion receiving said barrel portion,   cone-shaped panel driving said barrel portion into said portion, deforming said panel portion to conform generally to the shape of said polygonal barrel portion and into said axial grooves, and   deforming a free end of said barrel portion radially outwardly, forming a mechanical interlock between said barrel portion and said panel.   
     
     
       2. The method of attaching a female fastening element in a plastically deformable panel as defined in claim 1, wherein said body portion of said female fastening element includes an integral radially extending flange portion opposite said barrel portion and said grooves extending radially from said body portion into said flange portion, said method including driving said flange portion into said panel forming a generally flush mounting of said female fastening element in said panel and driving said panel into said radial grooves, preventing relative rotation of said female fastening element in said panel. 
     
     
       3. A method of attaching a fastening element in a plastically deformable panel, said fastening element including a body portion, an integral radially extending flange portion at one end of said body portion and an integral generally coaxially aligned annular cylindrical barrel portion extending from an opposite end of said body portion, said cylindrical annular barrel portion having a diameter less than said body portion, said barrel portion including a plurality of axially extending spaced grooves and said grooves extending radially from said body portion in said flange portion adjacent said body portion, said method comprising the following steps: forming an opening in said panel coaxially aligned with said barrel portion having a diameter less than an internal diameter of said cylindrical annular barrel portion,   driving a free end of said barrel portion against said panel, drawing said panel into a generally cone-shaped portion receiving said body portion,   driving said barrel portion into said cone-shaped panel portion, deforming said panel portion to conform generally to the exterior surface of said body portion and into said axial grooves,   deforming a free end of said annular barrel portion radially outwardly into locking engagement with said panel portion, and   driving said radial flange portion into said panel and said panel into said radial grooves, thereby preventing relative rotation of said fastening element in said panel.   
     
     
       4. The method of attaching a fastening element in a panel as defined in claim 7, wherein said body portion of said fastening element is polygonal having a plurality of flat surfaces and said axial grooves are defined in said body portion in the juncture of adjacent flat surfaces at the outside edges of said polygonal body portion, said method including driving said grooved edges of said body portion into said panel portion and said panel portion into said axial grooves, said grooves continuing into said flange portions and said method including continuing to drive said panel into said radial grooves, forming a continuous panel portion extending into said axial and radial grooves. 
     
     
       5. A method of attaching a self-attaching fastening element to a panel supported on a female die member having an annular concave die cavity, said self-attaching fastening element including a body portion, an integral radially extending flange portion at one end of said body portion and an integral annular tubular riveting barrel portion extending coaxially from an opposite end of said body portion, said body Portion including a plurality of spaced axial grooves extending generally parallel to a common axis of said body and barrel portions and said grooves extending from said body portion radially in said flange portion, said method including the following steps: forming an opening in said panel coaxially aligned with said barrel portion,   driving said annular tubular barrel portion through said panel opening,   driving said body portion into said panel adjacent said panel opening, thereby driving said panel into said axial grooves,   deforming a free end of said tubular barrel portion radially outwardly to form a mechanical interlock with said panel, and   driving said flange portion into said panel, deforming said panel into said radial grooves in said flange portion, thereby preventing relative rotation of said fastening element in said panel.   
     
     
       6. The method of attaching a self-attaching fastening element to a panel as defined in claim 5, wherein said fastening element is a female fastening element having a central bore coaxially aligned with said tubular barrel portion, said method including driving a punch through said body portion bore and said tubular barrel portion through said panel, said punch having an outside diameter less than an inside diameter of said tubular barrel portion forming a panel opening having a diameter less than said tubular barrel portion, then driving said tubular barrel portion against said panel, drawing a cone-shaped panel portion surrounding said panel opening receiving said body portion, then driving said body portion into said cone-shaped panel portion, deforming said panel portion to generally conform to the shape of said body portion and into said axial grooves. 
     
     
       7. The method of attaching said self-attaching fastening element to a panel as defined in claim 5, wherein said axial grooves in said fastening element body portion are continuous with said radial grooves in said flange portion, said method including deforming said panel into said axial grooves and continuing to deform said panel into said radial grooves, forming a continuous panel portion extending from said axial grooves into said radial grooves. 
     
     
       8. A female die assembly for attaching a self-riveting fastening element to a panel, said self-riveting fastening element including an annular barrel portion having internal and external surfaces, and a free open end, said female die assembly including a housing member having panel supporting surfaces on at least opposed sides and a central die member telescopically supported within said housing member between said panel supporting surfaces having a central die post and an annular concave die cavity surrounding said die post, said central die post having a convex arcuate outer surface blending into said concave die cavity and said die cavity having an outer arcuate concave die surface spaced from an outside surface of said die member and said panel supporting surfaces of said housing member, said die member spring-biased relative to said housing member to receive said annular barrel portion of said self-riveting fastening element in said annular concave die cavity, said annular die cavity adapted to deform said barrel portion radially outwardly to form a mechanical interlock with a panel supported on said panel supporting surfaces of said housing member. 
     
     
       9. The female die assembly defined in claim 8, characterized in that said central die member includes an axial bore through said central die post spaced from said annular die cavity.